Magnetic field sensor with improved response immunity

ABSTRACT

A magnetic field sensor includes a plurality of magnetoresistance elements, each having at least one characteristic selected to provide a respective, different response to an applied magnetic field, wherein each of the plurality of magnetoresistance elements is coupled in parallel. Illustrative characteristics selected to provide the respective responses include dimensions and/or construction parameters such as materials, layer thickness and order, and spatial relationship of the magnetoresistance element to the applied magnetic field. A method includes providing each of a plurality of magnetoresistance elements with at least one characteristic selected to provide a respective, different response to an applied magnetic field, wherein each of the plurality of magnetoresistance elements is coupled in parallel.

CROSS REFERENCE TO RELATED APPLICATIONS

Not Applicable.

STATEMENT REGARDING FEDERALLY SPONSERED RESEARCH

Not Applicable.

FIELD

This disclosure relates generally to magnetic field sensors, and moreparticularly, to a magnetic field sensor having an improved responseimmunity.

BACKGROUND

As is known, sensors of various types are used in a variety ofapplications. Sensors including one or more sensing elements (e.g.,pressure sensing elements, temperature sensing elements, light sensingelements, acoustic sensing elements, and magnetic field sensingelements) are used to detect one or more parameters (e.g., pressure,temperature, light, sound, magnetic field). Magnetic field sensors, forexample, are circuits including one or more magnetic field sensingelements, generally in combination with other circuit components (e.g.,analog, digital and/or mixed signal components), and are used to detecta magnetic field.

In motion (e.g., rotation) detectors, for example, a magnetic fieldsensor may be used to detect motion of an object, such as aferromagnetic object, for example, a gear or ring magnet. A magneticfield associated with the object is typically detected by one or moremagnetic field sensing elements, such as Hall effect elements and/ormagnetoresistance elements, which provide a signal (i.e., a magneticfield signal) proportional to an applied magnetic field.

Magnetic field sensing elements are typically sensitive to magneticfield strength and temperature. A magnetic field sensing element'sresponse to an applied magnetic field (e.g., a magnetic field as may beaffected by motion of a ferromagnetic object) may, for example, be afunction of various factors including design parameters, such asmaterials, layer thickness and other dimensions, etc. Manufacturingtolerances and/or defects or irregularities (e.g., layer thickness orlayer quality defects) formed during manufacture and/or use of magneticfield sensing elements may adversely affect a magnetic field sensingelement's expected response (e.g., change in resistance) to an appliedmagnetic field and, thus, adversely affect the reliability of aresulting device (e.g., motion detector) in which the magnetic fieldsensing elements are provided.

In high precision sensing applications such as automobiles, accuracy inmagnetic field sensing, such as may be used to detect motion of a targetobject, can be critical. Engine ignition timing, for example, depends onconsistent detection accuracy. When magnetic field sensing elements of amagnetic field sensor integrated circuit (IC) in an engine ignitiontiming system respond to a magnetic field in an unknown and/orundesirable manner, detection accuracy by the magnetic field sensor IC,and the resulting accuracy or performance of the engine ignition timingsystem, can be negatively impacted (e.g., due to sudden unexpectedchanges in an output of magnetic field sensing elements).

SUMMARY

Described herein are concepts, systems, circuits and techniques relatedto a magnetic field sensor and a method for providing such a sensor withan improved response to an applied magnetic field and therefore improvedsensing. More particularly, the resulting response can exhibit immunityto certain response deviations.

In one aspect of the concepts described herein, a magnetic field sensorincludes a plurality of magnetoresistance elements, each having at leastone characteristic selected to provide a respective, different responseto an applied magnetic field, wherein each of the plurality ofmagnetoresistance elements is coupled in parallel. With thisarrangement, a condition causing an unexpected or undesirable responsein one of the plurality of magnetoresistance elements will have areduced impact on the magnetic field sensor accuracy.

The magnetic field sensor may include one or more of the followingfeatures individually or in combination with other features. Therespective, different responses of the plurality of magnetoresistanceelements to the applied magnetic field may differ in linearity. Each ofthe plurality of magnetoresistance elements may have a substantiallysimilar resistance when the applied magnetic field has a magnetic fieldstrength of about zero Gauss. At least one of the plurality ofmagnetoresistance elements may experience a non-linear response to theapplied magnetic field. At least two of the plurality ofmagnetoresistance elements may experience a non-linear response to theapplied magnetic field. The non-linear response may be a result of amagnetic domain. The non-linear response experienced may also be aresult of the applied magnetic field having a strength greater than apredetermined level.

Each of the plurality of magnetoresistance elements may have arespective length and width and such length and width may comprise theat least one characteristic selected to provide the respective,different responses to the applied magnetic field. The length and widthof a first one of the plurality of magnetoresistance elements may be amultiple of the length and width of a second one of the plurality ofmagnetoresistance elements. The length and width of the first one of theplurality of magnetoresistance elements may also be approximatelyone-half the length and width of a second one of the plurality ofmagnetoresistance elements.

Each of the plurality of magnetoresistance elements may have arespective construction and the respective construction may comprise theat least one characteristic selected to provide the respective,different responses to the applied magnetic field. The respectiveconstruction may include one or more of: a material of one or morelayers of the magnetoresistance element, a thickness of one or morelayers of the magnetoresistance element, an ordering of one or morelayers of the magnetoresistance element, and a spatial relationship ofthe magnetoresistance element with respect to the applied magneticfield. The plurality of magnetoresistance elements may be coupled in abridge configuration.

The magnetic field sensor may include processing circuitry responsive toa magnetic field signal generated by the plurality of magnetoresistanceelements in response to the applied magnetic field and configured toprovide an output signal of the magnetic field sensor indicative of theapplied magnetic field. The output signal of the magnetic field sensormay be indicative of one or more of a strength of the applied magneticfield, an angle of the applied magnetic field, a current associated withthe applied magnetic field, and a speed and/or direction of movement ofa ferromagnetic element that affects the applied magnetic field.

The magnetic field sensor may include processing circuitry responsive toa plurality of magnetic field signals, each generated by a respectiveone or more of the plurality of magnetoresistance elements in responseto the applied magnetic field and configured to provide an output signalof the magnetic field sensor indicative of the applied magnetic field.The output signal of the magnetic field sensor may be indicative of oneor more of a strength of the applied magnetic field, an angle of adirection of the applied magnetic field, a current associated with theapplied magnetic field, and a movement of a ferromagnetic element thataffects the applied magnetic field. The magnetic field sensor may be acurrent sensor.

The plurality of magnetoresistance elements may include one or more of agiant magnetoresistance (GMR) element, a magnetic tunnel junction (MTJ)element and a tunneling magnetoresistance (TMR) element. The pluralityof magnetoresistance elements may include an anisotropicmagnetoresistance (AMR) element. The magnetic field sensor may include aplurality of current sources, each coupled to one or more of theplurality of magnetoresistance elements.

In another aspect of the concepts described herein, a method includesproviding each of a plurality of magnetoresistance elements with atleast one characteristic selected to provide a respective, differentresponse to an applied magnetic field, wherein each of the plurality ofmagnetoresistance elements is coupled in parallel.

The method may include one or more of the following features eitherindividually or in combination with other features. Providing each of aplurality of magnetoresistance elements may include providing the eachof the plurality of magnetoresistance elements with a response to theapplied magnetic field that differs in linearity. Providing each of aplurality of magnetoresistance elements may include providing at leastone magnetoresistance element that experiences a non-linear response tothe applied magnetic field. Providing each of a plurality ofmagnetoresistance elements may include providing at least twomagnetoresistance elements that experience a non-linear response to theapplied magnetic field.

Providing each of a plurality of magnetoresistance elements may includecoupling the plurality of magnetoresistance elements in a bridgeconfiguration. Providing each of a plurality of magnetoresistanceelements may include providing each of the plurality ofmagnetoresistance elements with a respective length and width, whereinsuch length and width comprise the at least one characteristic selectedto provide the respective, different responses to the applied magneticfield, and the length and width of a first one of the plurality ofmagnetoresistance elements may be a multiple of the length and width ofa second one of the plurality of magnetoresistance elements. The methodmay include providing a plurality of current sources, each coupled toone or more of the plurality of magnetoresistance elements.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing features of the disclosure, as well as the disclosureitself may be more fully understood from the following detaileddescription of the drawings, in which:

FIG. 1 is a block diagram of an example magnetic field sensor comprisinga plurality of magnetoresistance elements according to the disclosure;

FIG. 2 shows a first example configuration of a sensing circuit that mayform a portion of the magnetic field sensor of FIG. 1;

FIG. 2A shows a second example configuration of a sensing circuit thatmay form a portion of the magnetic field sensor of FIG. 1;

FIG. 2B shows a third example configuration of a sensing circuit thatmay form a portion of the magnetic field sensor of FIG. 1;

FIG. 3 shows an illustrative characteristic curve associated with asingle magnetoresistance element and an illustrative characteristiccurve associated with an example configuration comprising a plurality ofmagnetoresistance elements according to the disclosure;

FIG. 4 shows an example configuration of magnetoresistance elements asmay be provided in the magnetic field sensor of FIG. 1; and

FIG. 5 is a block diagram of another example magnetic field sensorcomprising a plurality of magnetoresistance elements according to afurther aspect of the disclosure.

DETAILED DESCRIPTION

The features and other details of the concepts, systems, and techniquessought to be protected herein will now be more particularly described.It will be understood that any specific embodiments described herein areshown by way of illustration and not as limitations of the disclosureand the concepts described herein. Features of the subject matterdescribed herein can be employed in various embodiments withoutdeparting from the scope of the concepts sought to be protected.Embodiments of the present disclosure and associated advantages may bebest understood by referring to the drawings, where like numerals areused for like and corresponding parts throughout the various views. Itshould, of course, be appreciated that elements shown in the figures arenot necessarily drawn to scale. For example, the dimensions of someelements may be exaggerated relative to other elements for clarity.

For convenience, certain introductory concepts and terms used in thespecification are collected here.

As used herein, the term “magnetic field domain” is used to describe aregion within a magnetic field sensing element in which magnetization ofthe magnetic material is in a uniform direction. In other words,individual magnetic moments of atoms within the magnetic material arealigned with each other in the region with the magnetic material andpoint in a same direction within the magnetic material. When a magneticdomain is aggravated and individual magnetic moments of atoms within amagnetic material are no longer aligned and pointing in a same direction(e.g., due to the magnetic material being subjected to a magnetic fieldhaving a having a strength greater than a predetermined level), themagnetic domain can cause the magnetic material and, thus, a magneticfield sensing element including the magnetic material, to have anon-linear response (e.g., experience a sudden jump in resistance) to anapplied magnetic field.

As used herein, the term “magnetic field sensor” is used to describe acircuit that uses one or more magnetic field sensing elements, generallyin combination with other components and/or circuits. Magnetic fieldsensors are used in a variety of applications, including, but notlimited to, an angle sensor that senses an angle of a magnetic field, acurrent sensor that senses a magnetic field generated by a currentcarried by a current-carrying conductor, a magnetic switch that sensesthe proximity of a ferromagnetic object, a rotation detector that sensespassing ferromagnetic articles, for example, magnetic domains of a ringmagnet or features of a ferromagnetic target (e.g., gear teeth) wherethe magnetic field sensor is used in combination with a back-biased orother magnet, and a so-called linear magnetic field sensor that senses amagnetic field density of a magnetic field.

As used herein, the term “magnetic field sensing element” is used todescribe a variety of electronic elements that can sense a magneticfield. The magnetic field sensing element can be, but is not limited to,a magnetoresistance element, a Hall effect element, or amagnetotransistor. As is known, there are different types ofmagnetoresistance (MR) elements, for example, a semiconductormagnetoresistance element such as Indium Antimonide (InSb), a giantmagnetoresistance (GMR) element, for example, a spin valve, ananisotropic magnetoresistance element (AMR), a tunnelingmagnetoresistance (TMR) element, and a magnetic tunnel junction (MTJ).As is also known, there are different types of Hall effect elements, forexample, a planar Hall element, a vertical Hall element, and a CircularVertical Hall (CVH) element. The magnetic field sensing element may be asingle element or, alternatively, may include two or more magnetic fieldsensing elements arranged in various configurations, e.g., a half bridgeor full (Wheatstone) bridge. Depending on the device type and otherapplication requirements, the magnetic field sensing element may be adevice made of a type IV semiconductor material such as Silicon (Si) orGermanium (Ge), or a type III-V semiconductor material likeGallium-Arsenide (GaAs) or an Indium compound, e.g., Indium-Antimonide(InSb).

As used herein, the term “processor” is used to describe an electroniccircuit that performs a function, an operation, or a sequence ofoperations. The function, operation, or sequence of operations can behard coded into the electronic circuit or soft coded by way ofinstructions held in a memory device. A “processor” can perform thefunction, operation, or sequence of operations using digital values orusing analog signals.

In some embodiments, the “processor” can be embodied, for example, in aspecially programmed microprocessor, a digital signal processor (DSP),or an application specific integrated circuit (ASIC), which can be ananalog ASIC or a digital ASIC. Additionally, in some embodiments the“processor” can be embodied in configurable hardware such as fieldprogrammable gate arrays (FPGAs) or programmable logic arrays (PLAs). Insome embodiments, the “processor” can also be embodied in amicroprocessor with associated program memory. Furthermore, in someembodiments the “processor” can be embodied in a discrete electroniccircuit, which can be an analog circuit, a digital circuit or acombination of an analog circuit and a digital circuit. The “controller”described herein may be provided as a “processor.”

As used herein, the term “motion” is used to describe a variety of typesof movement associated with an object, for example, including rotationalmovement (or “rotation”) and linear (or “rectilinear”) movement of theobject. A “motion detector” may, for example, detect rotation of anobject. A “rotation detector” is a particular type of “motion detector.”

Additionally, while parallel magnetoresistance elements including acertain number of magnetoresistance elements (e.g., two or three)coupled in parallel are described in several examples below, it shouldbe appreciated that the concepts, systems, circuits and techniquesdisclosed herein may be implemented using more than or less than thecertain number of magnetoresistance elements coupled in parallel.

Further, it should be appreciated that, as used herein, relationalterms, such as “first,” “second,” “top,” “bottom,” “left,” “right,” andthe like, may be used to distinguish one element or portion(s) of anelement from another element or portion(s) of the element withoutnecessarily requiring or implying any physical or logical relationshipor order between such elements.

Referring now to FIG. 1, an example magnetic field sensor system 100includes a magnetic field sensor 130 having a plurality of magneticfield sensing elements 140 coupled in parallel and configured to providean output signal 170 a in response to an applied magnetic field (e.g., amagnetic field as may be generated by an object 120, as will bediscussed).

The magnetic field sensor 130, which may be provided in the form of anintegrated circuit (IC) in some embodiments, includes a signal path, orchannel 150 (e.g., an analog, digital or mixed signal path). The sensor130 also includes a memory device 160 (e.g., EEPROM or flash memory),and a controller 170. The signal path 150 has an input coupled to anoutput of the parallel magnetic field sensing elements 140, and anoutput coupled to the controller 170.

The parallel magnetic field sensing elements 140 may be driven by one ormore current and/or voltage sources (not shown) and include a pluralityof magnetoresistance (MR) elements (e.g., GMR elements) coupled inparallel to form a parallel MR resistance. The parallel magnetic fieldsensing elements 140 may also include at least one other type ofmagnetic field sensing element (e.g., Hall effect element) in additionto the magnetoresistance elements in some embodiments. The other type ofmagnetic field sensing element may be coupled in series or in parallelwith the with parallel magnetoresistance elements 140. Further, thespecific type of other magnetic field sensing element (e.g., verticalHall effect element) may be selected such that the other magnetic fieldsensing element has a same or similar axis of sensitivity as parallelmagnetoresistance elements 140.

The applied magnetic field may be generated in various ways depending onthe type of sensor system 100 and its application. For example, theapplied magnetic field may be generated in response to motion of anobject 120 (e.g., a ring magnet or ferromagnetic gear) having features,e.g., magnetic domains or gear teeth 120 a, 120 b, 120 c, 120 d. Forexample, the object 120 can be disposed a shaft 110 (e.g., a steeringshaft or a camshaft) configured to rotate in a direction 112. The object120 may also be coupled to an automobile wheel, as another example. Theapplied magnetic field may also be generated by a magnet (not shown)disposed proximate to or within the sensor 130. With such a back-biasedmagnet configuration, motion of the object 120 can result in variationsof the magnetic field sensed by the parallel magnetoresistance elements140 and, thus, may result in variations of the magnetic field signal 140a. It should be appreciated that the parallel magnetoresistance elements140 may take any form and configuration suitable for detecting motion(e.g., speed of motion and/or direction of motion) of the object 120 bysensing a magnetic field affected by such motion.

Each of the parallel magnetoresistance elements 140 has at least onecharacteristic (e.g., length, width and/or construction, as will bediscussed further below) selected to provide a respective, differentresponse (e.g., change in resistance) to the applied magnetic field. Therespective, different responses of the parallel magnetoresistanceelements 140 to the applied magnetic field may, for example, differ inlinearity, and correspond to at least one of the parallelmagnetoresistance elements 140 experiencing a different, non-linearresponse to the applied magnetic field and/or a magnetic domain. Inother words, each of the parallel magnetoresistance elements 140 mayhave a different susceptibility to response variations, such as may bedue to the applied magnetic field and/or a magnetic domain. Theforegoing may, for example, reduce the impact of magnetic domainsassociated with individual magnetoresistance elements of the parallelmagnetoresistance elements 140. As known, due to manufacturingconstraints and tolerances magnetic domains and responses to aparticular magnetic field strength can differ even amongstmagnetoresistance elements intended to be identical.

In some embodiments, the parallel magnetoresistance elements 140 mayinclude one or more of a giant magnetoresistance (GMR) element, amagnetic tunnel junction (MTJ) element and a tunneling magnetoresistance(TMR) element. Additionally, in some embodiments, the parallelmagnetoresistance elements 140 may include an anisotropicmagnetoresistance (AMR) element. In one embodiment, it is preferable forthe parallel magnetoresistance elements 140 to be of a same or similarelement type (e.g., GMR elements) with each of the parallelmagnetoresistance elements 140 having the at least one characteristicselected to provide the respective, different response to the appliedmagnetic field.

The signal path 150, which includes an amplifier 152, a filter 154 andan analog-to-digital converter (ADC) 156 in the illustrated embodiment,is coupled to receive the magnetic field signal 140 a at an input andconfigured to generate a signal (e.g., digital signal 156 a)representative of the magnetic field signal 140 a at an output. Inparticular, the amplifier 152 is coupled to receive the magnetic fieldsignal 140 a and configured to generate an amplified signal 152 a.Additionally, the filter 154 (e.g., a programmable analog filter) iscoupled to receive the amplified signal 152 a and configured to generatea filtered signal 154 a. Further, the ADC 156 is coupled to receive thefiltered signal 154 a and configured to generate a corresponding digitalsignal 156 a. The digital signal 156 a is provided to a correspondinginput of controller 170.

The controller 170 (e.g., a synchronous digital controller or an analogcontroller), which may include diagnostic circuitry and/or software, forexample, is coupled to receive at least the digital signal 156 a at arespective input and configured to generate a controller output signal170 a at an output of the sensor 130. The controller output signal 170 acan be provided in a variety of signal formats, including, but notlimited to, a SENT format, an I²C format, a PWM format, or a two-statebinary format, and may be provided as a signal indicative of themagnetic field signal 140 a (i.e., a signal indicative of the appliedmagnetic field). The controller output signal 170 a may also be providedas a signal indicative of one or more of a strength of the appliedmagnetic field, a proximity of a target, an angle of the appliedmagnetic field, a current associated with the applied magnetic field,and a movement characteristic, such as speed and/or direction, of aferromagnetic element (e.g., object 120) that affects the appliedmagnetic field. In some embodiments, the controller output signal 170 amay be received by circuitry (e.g., analog, digital or mixed-signalcircuitry) (not shown) for further processing (e.g., for generatingfiltered signals, amplified signals, and the like) and error reporting(e.g., to an engine control unit or ECU). For example, in the context ofa magnetic field sensor that provides a speed indicating output signal170 a, the controller 170 may include a peak detector that compares adigital version 156 a of the magnetic field sensor signal 140 a to athreshold signal. It will be appreciated that other processing circuitrycan be provided in the controller 170 according to the desiredinformation to be provided in the output signal 170 a.

While the sensor 130 may be provided in the form of an integratedcircuit with an analog front end portion and a digital portion, it willbe appreciated that the particular delineation of which circuitfunctions are implemented in an analog fashion or with digital circuitryand signals can be varied. For example, one or more portions of thesignal path 150 (e.g., amplifier 152, filter 154, ADC 156) may beprovided as part of the controller 170. The controller 170 can, forexample, perform the function, operation, or sequence of operations ofone or more portions of the signal path 150. Additionally, the memorydevice 160 can be provided as part of the controller 170 (e.g., asonboard EEPROM). Further, some of the illustrated circuit functions canbe implemented on separate circuits (e.g., additional substrates withinthe same integrated circuit package, or additional integrated circuitpackages, and/or on circuit boards).

Referring to FIGS. 2-2B, example sensing circuits as may be provided ina magnetic field sensor, such as the sensor 130 of FIG. 1 are shown. Itshould be appreciated that the example sensing circuits described beloware but several of many potential configurations of sensing circuits inaccordance with the concepts, systems, circuits and techniques describedherein.

Referring to FIG. 2, an example sensing circuit 280 includes a pluralityof magnetoresistance elements 242, 242′, 242″ (e.g., GMR elements), asignal path 250, and a current source 232. The magnetoresistanceelements 242, 242′, 242″, which may be the same as or similar to theparallel magnetoresistance elements 140 of FIG. 1, are coupled inparallel and are referenced collectively by numeral 240. The parallelmagnetoresistance elements 240 have a first terminal coupled to thecurrent source 232 and a second terminal coupled to a second terminal202 of the sensing circuit 280. Current source 232 (e.g., a constant orvariable current source) is disposed in a signal path between a firstterminal 201 of the sensing circuit 280 and the first terminal of theparallel magnetoresistance elements 240. Additionally, the signal path250 has an input coupled to a node N between the first and secondterminals 201, 202 of the sensing circuit 280, and an output coupled toan output of the sensing circuit 280. The signal path 250 is shown withdotted lines to illustrate that in some embodiments, the signal path 250can be external to the sensing circuit 280.

The parallel magnetoresistance elements 240, which may be used, forexample, to provide an output signal of a magnetic field sensor (e.g.,130, shown in FIG. 1) in response to an applied magnetic field (e.g., amagnetic field as may be generated by object 120 of FIG. 1), are drivenby the current source 232. The current source 232 is coupled to a supplyvoltage, denoted as VCC at the first terminal 201 of the sensing circuit280, as may be received from a power supply (not shown), and isconfigured to drive the parallel magnetoresistance elements 240 with acorresponding current.

Each of the parallel magnetoresistance elements 240 has at least onecharacteristic (e.g., length, width and/or construction) selected toprovide a respective, different response (e.g., change in resistance) toan applied magnetic field. The respective, different response of theparallel magnetoresistance elements 240 to the applied magnetic fieldmay, for example, differ in linearity. In one embodiment, each of theparallel magnetoresistance elements 240 has a substantially similarresistance when the applied magnetic field has a magnetic field strengthof about zero Gauss. Additionally, in one embodiment, at least one ofthe parallel magnetoresistance elements 240 experiences a non-linearresponse to the applied magnetic field. Further, in one embodiment, atleast two of the parallel magnetoresistance elements 240 experience anon-linear response in response to the applied magnetic field. Thenon-linear response may, for example, be a result of a magnetic domain.In other words, each of the parallel magnetoresistance elements 240 mayexperience a respective, different response (e.g., have a differentimmunity) to the magnetic domain. The non-linear response may also be aresult of the applied magnetic field having a strength greater than apredetermined level. In other words, each of the parallelmagnetoresistance elements 240 may experience a respective, differentresponse to the applied magnetic field having a strength greater thanthe predetermined level. The predetermined level may, for example, bebased on type of the parallel magnetoresistance elements 240 (e.g., GMRor AMR elements).

Beyond having the at least one characteristic selected to provide therespective, different response to the applied magnetic field, theparallel magnetoresistance elements 240 may be the same as or similar toeach other (e.g., in dimensions and/or construction) or may be differentfrom each other. However, each of the parallel magnetoresistanceelements 240 will have at least one characteristic selected to bedifferent to provide the respective, different response to the appliedmagnetic field.

Changes in the applied magnetic field experienced by the parallelmagnetoresistance elements 240 may cause the resistance (e.g., totalresistance or parallel MR resistance) of the parallel magnetoresistanceelements 240 to change. Additionally, in some embodiments, changes intemperature experienced by the parallel magnetoresistance elements 240may also cause the resistance of the parallel magnetoresistance elements240 to change. As the resistance of the parallel magnetoresistanceelements 240 changes, a voltage at node N (i.e., 242 a) also changes.Additionally, as the resistance of the parallel magnetoresistanceelements 240 changes, an output of the sensing circuit 280 (e.g.,amplifier output signal 252 a) and an output of a sensor (e.g., 130) inwhich the sensing circuit 280 may be provided may also change.

Since magnetoresistance elements 242, 242′, 242″ are coupled in parallelin the example embodiment shown, the total resistance (i.e., R_(total))or parallel MR resistance of the parallel magnetoresistance elements 240is equal to R₂₄₂∥R_(242′)∥R_(242″), or

$\frac{R_{242} \times R_{242^{\prime}} \times R_{242^{''}}}{\left( {R_{242} \times R_{242^{\prime}}} \right) + \left( {R_{242} \times R_{242^{''}}} \right) + \left( {R_{242^{\prime}} \times R_{242^{''}}} \right)},$

where R₂₄₂ corresponds to a resistance associated with magnetoresistanceelement 242, R_(242′) corresponds to a resistance associated withmagnetoresistance element 242′, and R_(242″) corresponds to a resistanceassociated with magnetoresistance element 242″. As one example result ofthis arrangement, in embodiments where one or more of the parallelmagnetoresistance elements 240 (e.g., magnetoresistance element 242)experiences a non-linear response to the applied magnetic field (e.g.,due to a magnetic domain or the applied magnetic field having a strengthgreater than a predetermined level), the total resistance of theparallel magnetoresistance elements 240 is minimally affected by thenon-linear response of the one or more parallel magnetoresistanceelements 240 to the applied magnetic field. It follows that the voltageat node N (i.e., 242 a), the output of the sensing circuit 280, and theoutput of the sensor in which the sensing circuit 280 may be provided,likewise may be minimally affected by the non-linear response of the oneor more parallel magnetoresistance elements 240 to the applied magneticfield. Detection accuracy of the sensing circuit 280 can thereby beimproved over conventional arrangements.

In other words, in contrast to conventional arrangements in which only asingle magnetoresistance element is used, which single element mayexperience a non-linear response to an applied magnetic field, theparallel magnetoresistance elements 240 in the above-describedarrangement may experience a reduced change in total resistance (e.g., areduced impact from a magnetic domain) as a result of the parallelcoupling of magnetoresistance elements 242, 242′, 242″ that have atleast one characteristic (e.g., length, width and/or construction)selected to provide a respective, different response to the appliedmagnetic field.

For example, if magnetoresistance element 242 of the parallelmagnetoresistance elements 240 in the above-described arrangementexperiences a non-linear response to an applied magnetic field due to amagnetic domain, the total resistance of the parallel magnetoresistanceelements 240 may be given by (R₂₄₂+R_(domain))∥R_(242′)∥R_(242″), or

$\frac{\left( {R_{242} + R_{domain}} \right) \times R_{242^{\prime}} \times R_{242^{''}}}{\begin{matrix}{\left( {\left( {R_{242} + R_{domain}} \right) \times R_{242^{\prime}}} \right) +} \\{\left( {\left( {R_{242} + R_{domain}} \right) \times R_{242^{''}}} \right) + \left( {R_{242^{\prime}} \times R_{242^{''}}} \right)}\end{matrix}},$

where R_(domain) corresponds to the resistance change due to themagnetic domain. As illustrated, magnetoresistance elements 242′ and242″ mask (or minimize) the impact of the magnetic domain on the totalresistance of the parallel elements. In contrast, if only themagnetoresistance element 242 were used, the resulting resistance wouldbe given by R₂₄₂+R_(domain).

The signal path 250, which may be the same as or similar to signal path150 described above in conjunction with FIG. 1, for example, isconfigured to provide an output signal (e.g., amplifier output signal252 a) of the sensing circuit 280. The signal path 250 includes anamplifier 252 which may be the same as or similar to amplifier 152 ofsignal path 150 and may be powered by the supply voltage received atfirst terminal 201 of the sensing circuit 280 and coupled to receive avoltage 242 a associated with magnetoresistance elements 240 at a firstamplifier input (e.g., a non-inverting input). The amplifier 252 is alsocoupled to receive a reference signal (e.g., a ground or non-zeroreference voltage) at a second amplifier input (e.g., an invertinginput) and configured to generate an amplifier output signal 252 aindicative of a voltage difference between the voltage 242 a and thereference signal. The amplifier output signal 252 a corresponds to anoutput signal of the sensing circuit 280 in the illustrated embodiment.

In some embodiments, the output of sensing circuit 280 (here, amplifieroutput signal 252 a) may be received at an input of circuitry (e.g.,controller 170) for further processing (e.g., to provide an output of asensor IC). Additionally, in some embodiments, signal path 250 includescircuitry (e.g., proximity detector circuitry) to determine the speed,direction, proximity, angle, etc. of an object (e.g., 120, shown inFIG. 1) based on changes in the applied magnetic field, and responses ofthe parallel magnetoresistance elements 240 to the applied magneticfield.

Referring to FIG. 2A, a sensing circuit 1280 in accordance with anotherembodiment includes magnetoresistance elements 242, 242′ and signal path250. The sensing circuit 1280 also includes additional magnetoresistanceelements 1242, 1242′, 2242, 2242′, 3242, 3242′ in the illustratedembodiment. Magnetoresistance elements 242, 242′, 1242, 1242′, 2242,2242′, 3242, 3242′ are coupled in a bridge configuration (e.g., aWheatstone bridge configuration), as denoted by reference numeral 1240.The bridge configuration 1240 has a first terminal coupled to firstterminal 201 of sensing circuit 1280 and a second terminal coupled tosecond terminal 202 of sensing circuit 1280.

Each of the magnetoresistance elements of FIG. 2A is coupled in parallelwith at least one other magnetoresistance element. In particular,magnetoresistance element 242′ is coupled in parallel withmagnetoresistance element 242, magnetoresistance element 1242′ iscoupled in parallel with magnetoresistance element 1242,magnetoresistance element 2242′ is coupled in parallel withmagnetoresistance element 2242, and magnetoresistance element 3242′ iscoupled in parallel with magnetoresistance element 3242. In someembodiments, more than two magnetoresistance elements may be coupled inparallel with each other, as shown in FIG. 2, for example. Each “arm” ofthe bridge configuration 1240 contains a same number ofmagnetoresistance elements (e.g., two) coupled in parallel, as shown inFIG. 2A, for example. However, in other embodiments, it is possible forat least one “arm” of the bridge configuration 1240 to contain adifferent number of magnetoresistance elements coupled in parallel thanother “arms” of the bridge configuration 1240.

The parallel magnetoresistance elements of FIG. 2A each have at leastone characteristic (e.g., length, width and/or construction) selected toprovide a respective, different response (e.g., change in resistance) toan applied magnetic field in some embodiments. The foregoing may, forexample, provide for each of the magnetoresistance elements of FIG. 2Ahaving a different immunity to a magnetic domain, as discussed above inconjunction with FIG. 2. In other embodiments, each magnetoresistanceelement in a parallel-coupled pair or group of magnetoresistanceelements (e.g., 242, 242′) has at least one characteristic selected toprovide a respective, different response to the applied magnetic field,but magnetoresistance elements in different parallel-coupled groups ofmagnetoresistance elements may have the same or similar response. Forexample, magnetoresistance elements 242, 1242, which are not coupled inparallel in the illustrated embodiment, may have a same or similarresponse to the applied magnetic field in some embodiments. Theforegoing may provide for each of the magnetoresistance elements of FIG.2A (e.g., 242, 242′, 1242) in a parallel-coupled pair or group ofmagnetoresistance elements having a different immunity to a magneticdomain. In one embodiment, it is preferable for each parallel-coupledpair or group of magnetoresistance elements to have a same or similarimmunity response to the applied magnetic field (e.g., such that aprobability of occurrence of a magnetic domain condition with one ormore of the magnetoresistance elements is normalized).

Amplifier 252 of signal path 250 is coupled to receive a first outputvoltage 1242 a generated at a first voltage node of the bridgeconfiguration 1240 at a first amplifier input (e.g., non-invertinginput), a second output voltage 1242 b generated at a second voltagenode of the bridge configuration 1240 at a second amplifier input (e.g.,an inverting input), and configured to generate an amplifier outputsignal 1252 a indicative of a voltage difference between the firstoutput voltage 1242 a and the second output voltage 1242 b. Amplifieroutput signal 1252 a may correspond to an output signal of the sensingcircuit 1280.

As the resistance of the magnetoresistance elements in bridgeconfiguration 1240 changes in response to an applied magnetic field asmay be produced by motion of an object (e.g., 120, shown in FIG. 1), forexample, at least one of the first output voltage 1242 a and the secondoutput voltage 1242 b may also change. The changes in the first outputvoltage 1242 a and/or the second output voltage 1242 b may be used todetect changes in the applied magnetic field. Since each of themagnetoresistance elements in at least a parallel-coupled pair or groupof magnetoresistance elements has at least one characteristic selectedto provide a respective, different response to the applied magneticfield, detection accuracy of the applied magnetic field may be minimallyaffected by an unexpected or undesirable (e.g., non-linear) response ofone or more of the magnetoresistance elements to the applied magneticfield.

While the magnetoresistance elements of FIG. 2A (e.g., 242, 242′, 1242)are shown coupled in a bridge configuration 1240 in the exampleembodiment shown, other arrangements are possible, for example, aresistor divider arrangement. Other possible arrangements include anarrangement in which the magnetoresistance elements are used as loadresistors in an amplifier stage, a half-bridge circuit comprising themagnetoresistance elements, and a circuit including at least oneparallel-coupled pair or group of magnetoresistance elements which arecoupled to a current source. Many other arrangements are, of course,possible, as will be apparent to one of skill in the art.

Referring to FIG. 2B, in which like elements of FIGS. 2 and 2A areprovided having like reference designations, a sensing circuit 2280 inaccordance with another embodiment includes magnetoresistance elements242, 242′, 1242, 1242′, 2242, 2242′, 3242, 3242′ and signal path 250.The sensing circuit 2280 also includes current sources 232, 232′, 1232,1232′, 2232, 2232′, 3232, 3232′ in the illustrated embodiment. Currentsources 232, 232′, 1232, 1232′, 2232, 2232′, 3232, 3232′, which may bethe same as or similar to each other in some embodiments, are eachcoupled to one or more of the magnetoresistance elements 242, 242′,1242, 1242′, 2242, 2242′, 3242, 3242′ and in a bridge configuration(e.g., a Wheatstone bridge configuration), as denoted by referencenumeral 2240.

The current sources of FIG. 2B are each coupled to receive the supplyvoltage, denoted as VCC, at the first terminal 201 of the sensingcircuit 2280, and are configured to drive the magnetoresistance elementswith corresponding current signals. The magnitude of these currentsignals may, for example, be adjusted to bias one or more of themagnetoresistance elements to provide for improved accuracy in thesensing circuit 2280 (e.g., by providing temperature compensation in thesensing circuit 2280). As one example, temperature compensation may beprovided in sensing circuit 2280 by adjusting the magnitude of thecurrent signals to maintain a same or similar voltage level at one ormore voltage nodes in the sensing circuit 2280 (e.g., a first voltagenode, as will be discussed) regardless of temperature. Although thecurrent sources of FIG. 2B (e.g., 232) are each shown as coupled to asingle magnetoresistance element (e.g., 242) in the illustratedembodiment, it should be appreciated that in other embodiments one ormore of the current sources of FIG. 2B may be coupled to two or moremagnetoresistance elements.

Amplifier 252 of signal path 250 is coupled to receive a first outputvoltage 2242 a generated at a first voltage node of the bridgeconfiguration 2240 at a first amplifier input (e.g., non-invertinginput), a second output voltage 2242 b generated at a second voltagenode of the bridge configuration 2240 at a second amplifier input (e.g.,inverting input), and is configured to generate an amplifier outputsignal 2252 a indicative of a voltage difference between the firstoutput voltage and the second output voltage. Amplifier output signal2252 a corresponds to an output signal of the sensing circuit 2280 inthe illustrated embodiment.

While the sensing circuits of FIGS. 2-2B are shown as including acertain number of magnetoresistance elements with the magnetoresistanceelements positioned in a particular manner, it should be appreciatedthat other configurations of magnetoresistance elements are possible inaccordance with the concepts, systems, circuits and techniques sought tobe protected herein. The circuits may be implemented using more than orless than the number of magnetoresistance elements shown, and themagnetoresistance elements may be configured in other manners than thatwhich is shown.

Referring to FIG. 3, illustrative characteristic curves as may berepresentative of response characteristics of magnetoresistanceelements, which can be the same as or similar to the magnetoresistanceelements described above in conjunction with FIGS. 1-2B, for example,are shown in a plot 300. The magnetoresistance elements can be provided,for example, in a magnetic field sensor which can be the same as orsimilar to magnetic field sensor 130 of FIG. 1. Plot 300 has ahorizontal axis with a scale in degrees corresponding, for example, torotation of an object (e.g., object 120, shown in FIG. 1) with respectto the magnetoresistance elements, and a vertical axis with a scale inohms corresponding to resistance of the magnetoresistance elements.

Plot 300 includes a first characteristic curve 310 representative of aresponse characteristic of a single magnetoresistance element (e.g.,242), and a second characteristic curve 320 representative of a combinedresponse characteristic of a plurality of magnetoresistance elements(e.g., 242, 242′, 242″) coupled in parallel (e.g., 240), for example, asshown in FIGS. 2-2B, when subjected to a magnetic field (e.g., anapplied magnetic field).

Curve 310 is represented by a line with markings (e.g., circle markings)and overlaps curve 320, which is represented by a line without markings,for a substantial portion of the plot 300, as will be discussed below.Each of the parallel-coupled magnetoresistance elements characterized bycurve 320 has at least one characteristic (e.g., length, width and/orconstruction) selected to provide a respective, different response to anapplied magnetic field. The plurality of magnetoresistance elementscharacterized by curve 320 may include the magnetoresistance elementcharacterized by curve 310.

As illustrated, the resistance of the magnetoresistance elementcharacterized by curve 310 and the resistance (e.g., total resistance)of the parallel magnetoresistance elements characterized by curve 320generally change in response to changes in a magnetic field strengthexperienced by the magnetoresistance element(s), except for when themagnetoresistance element(s) is/are in a so-called saturation region inwhich the resistance of the magnetoresistance element(s) substantiallylevels off.

As is also illustrated, the curves 310 and 320 are substantially thesame (and the magnetoresistance element(s) characterized by the curves310 and 320 have substantially the same resistance) until themagnetoresistance element(s) experience a first magnetic field strength, for example, at a first rotation position of the object, asrepresented by point 302. At point 302, the magnetoresistance elementcharacterized by curve 310 experiences a sudden increase in resistance,while the combined resistances of parallel-coupled magnetoresistanceelements characterized by curve 320 continue to decrease. In the exampleembodiment shown, the magnetoresistance element characterized by curve310 experiences an increase in resistance from the first magnetic fieldstrength at point 302 until a second, different magnetic field strength,for example, at a second rotation position of the object, as representedby point 303. At point 303, the magnetoresistance element characterizedby curve 310 experiences a sudden decrease in resistance. Additionally,at point 304, which corresponds to a third, different magnetic fieldstrength, for example, experienced by the magnetoresistance element(s)at a third rotation position of the object, curves 310 and 320 meetagain, with the magnetoresistance element(s) characterized by curves 310and 320 having a substantially similar resistance at the third magneticfield strength.

The sudden resistance changes illustrated by curve 310 relative to curve320 between points 302 and 304 may, for example, correspond to themagnetoresistance element characterized by curve 310 experiencing asubstantial non-linear response to the applied magnetic field (e.g., dueto a magnetic domain or the applied magnetic field having a strengthgreater than a predetermined level), while the combined resistance ofthe parallel-coupled magnetoresistance elements characterized by curve320, which may include the magnetoresistance element characterized bycurve 310, is substantially immune to the adverse responsecharacteristic of one of its constituent parallel-coupled elements. Forexample, parallel magnetoresistance elements characterized by curve 320may experience a slightly non-linear response or may even remainsubstantially linear due to the parallel coupling of itsmagnetoresistance elements. The foregoing may provide for improveddetection accuracy by the parallel magnetoresistance elements and, moreimportantly, detection accuracy of a magnetic field sensor in which theparallel magnetoresistance elements may be provided.

Referring to FIG. 4, an example plurality of magnetoresistance elements442, 442′, 442″ as may be coupled in parallel and provided in a magneticfield sensor (FIG. 1) is shown. Magnetoresistance elements 442, 442′,442″ (e.g., GMR yokes or yoke structures), which may be the same as orsimilar to magnetoresistance elements 242, 242′, 242″ of FIG. 2, arecoupled in parallel and supported by a substrate (not shown). Thesubstrate may be a semiconductor substrate or any other materialsubstrate that can support electrical components and may be provided inthe form of an integrated circuit. It is also possible that theparallel-coupled magnetoresistance elements may be provided on separateelectrically coupled substrates within the same integrated circuitpackage. Similar to the magnetoresistance elements described above, eachof the magnetoresistance elements has at least one characteristic (e.g.,dimensions and/or construction) selected to provide a respective,different response to an applied magnetic field.

In the example embodiment shown, each of the magnetoresistance elements442, 442′, 442″ has a respective length and width. Additionally, each ofthe magnetoresistance elements 442, 442′, 442″ has a first major surface(e.g., 443, 443′, 443″) and a second opposing major surface (not shown).The second major surface may be parallel, or parallel withinmanufacturing tolerances, to the respective first major surface. A firstdimension across first major surface 443 (e.g., a major axis of thefirst major surface 443) of a first one of the magnetoresistanceelements 442 may correspond to a length of the first magnetoresistanceelement 442 and a second dimension across the first major surface 443(e.g., a minor axis of the first major surface 443) may correspond to awidth of the first magnetoresistance element 442. Additionally, a firstdimension across a first major surface 443′ of a second one of themagnetoresistance elements 442′ may correspond to a length of the secondmagnetoresistance element 442′ and a second dimension across the firstmajor surface 443′ may correspond to a width of the secondmagnetoresistance element 442′. Further, a first dimension across afirst major surface 443″ of a third one of the magnetoresistanceelements 442″ may correspond to a length of the third magnetoresistanceelement 442″ and a second dimension across the first major surface 443″may correspond to a width of the third magnetoresistance element 442″.

The above-described length and width dimensions of the magnetoresistanceelements 442, 442′, 442″ may comprise the at least one characteristicselected to provide the respective, different responses (e.g.,corresponding changes in resistance) to the applied magnetic field insome embodiments. As one example, the length and width of firstmagnetoresistance element 442 may be a multiple of the length and widthof second magnetoresistance element 442′. Additionally, the length andwidth of second magnetoresistance element 442′ may be a multiple of thelength and width of third magnetoresistance element 442″. For example,the length and width of first magnetoresistance element 442 may beapproximately one-half the length and width of second magnetoresistanceelement 442′. Additionally, the length and width of secondmagnetoresistance element 442′ may be approximately one-half the lengthand width of third magnetoresistance element 442″. Other multiples(e.g., one-third, one-fourth, etc.) of the lengths and widths of themagnetoresistance elements 442, 442′, 442″ are possible.

In one embodiment, it is preferable for the magnetoresistance elements442, 442′, 442″ to each have the characteristic (e.g., length and/orwidth) selected to be different in order to provide the respective,different response to the applied magnetic field, as in the aboveexample in which each of the magnetoresistance elements 442, 442′, 442″has a different length and width than the other magnetoresistanceelements. In another embodiment, two of the magnetoresistance elements442, 442′, 442″ may have a first characteristic (e.g., length and/orwidth) selected to be different while one of the magnetoresistanceelements may have a second characteristic (e.g., construction) selectedto be different. For example, magnetoresistance elements 442, 442′ mayeach have lengths and widths selected to be different than each other,while magnetoresistance element 442″ may have a same length and width asone of the magnetoresistance elements 442, 442′ but have a construction(e.g., layer stack up) selected to be different.

The respective lengths and widths of the magnetoresistance elements 442,442′, 442″ may also be selected such that each magnetoresistance element442, 442′, 442″ has at least one different dimension (e.g., length),while also retaining a substantially similar resistance when subjectedto substantially no magnetic field (i.e., a magnetic field with astrength of about zero Gauss). For example, each of themagnetoresistance elements 442, 442′, 442″ may have a same or similarwidth but have a different length to provide for a substantially similarresistance when subjected to substantially no magnetic field. In thisscenario, the length may comprise the at least one characteristicselected to provide the respective, different responses to the appliedmagnetic field. Alternatively, the width may comprise the at least onecharacteristic selected to provide the respective, different responsesto the applied magnetic field while the lengths of the parallel-coupledelements may be substantially the same.

In general, the respective lengths and widths of the magnetoresistanceelements 442, 442′, 442″ may be any lengths and widths that provide fora respective, different response to an applied magnetic field.Additionally, the lengths and widths of the magnetoresistance elements442, 442′, 442″ can be made to have any dimensions within manufacturingcapabilities to achieve any desired resistance, and provide for therespective, different response to the applied magnetic field.

In some embodiments, one or more parameters associated with theconstruction of each of the magnetoresistance elements 442, 442′, 442″may comprise the at least one characteristic selected to provide therespective, different responses to the applied magnetic field.Illustrative construction parameters include one or more of: a material,a layer thickness, and a ordering of one or more layers (e.g.,antiferromagnetic layers, pinned layers and/or non-magnetic layers) ofthe magnetoresistance elements 442, 442′, 442″. The respectiveconstruction may also include a spatial relationship of themagnetoresistance elements 442, 442′, 442″ on one plane, for example,relative to an applied magnetic field. For example, magnetoresistanceelements 442, 442′, 442″ may each be supported by a semiconductorsubstrate with magnetoresistance element 442 positioned closer to anedge of the substrate than magnetoresistance element 442′ andmagnetoresistance element 442′ positioned closer to the edge of thesubstrate than magnetoresistance element 442″.

As one example, magnetoresistance elements 442, 442′, 442″ may eachcomprise multiple layers (i.e., a material stack) including one or moreantiferromagnetic layers, one or more pinned layers, and/or one or morenon-magnetic layers. The antiferromagnetic layers may includeManganese-Platinum (MnPt), the pinned layers may include Cobalt-Iron(CoFe), and the non-magnetic layers may include a select one of Iridium(Ir) and Ruthenium (Ru) as a few examples.

In general, the material, layer thickness, and ordering of the layers(e.g., antiferromagnetic and non-magnetic layers) of themagnetoresistance elements 442, 442′, 442″ can affect the manner inwhich the magnetoresistance elements 442, 442′, 442″ respond to anapplied magnetic field.

Referring to FIG. 5, in which like elements of FIG. 1 are providedhaving like reference designations, a magnetic field sensor system 500in accordance with another embodiment includes a magnetic field sensor530, as may be provided in the form of an integrated circuit (IC). Thesensor 530 includes magnetic field sensing element(s) 540, magneticfield sensing element(s) 1540 and magnetic field sensing element(s)2540, each of which includes at least one magnetoresistance element(e.g., a GMR element). The sensor 530 additionally includes respectivesignal paths, or channels 150, 1150 and 2150. The signal path 150 has aninput coupled to an output of magnetic field sensing element(s) 540 andan output coupled to a corresponding input of a controller 170.Additionally, the signal path 1150 has an input coupled to an output ofmagnetic field sensing element(s) 1540 and an output coupled to acorresponding input of the controller 170. Further, the signal path 2150has an input coupled to an output of magnetic field sensing element(s)2540 and an output coupled to a corresponding input of the controller170.

Magnetic field sensing element(s) 540, which includes at least onemagnetoresistance element (e.g., a GMR element), may be driven by afirst current source (not shown) and configured to generate a magneticfield signal (e.g., magnetic field signal 540 a) in response to anapplied magnetic field (e.g., a magnetic field as may be generated bymotion of object 120).

Magnetic field sensing element(s) 540 may also include at least oneother type of magnetic field sensing element (e.g., Hall effect element)in addition to the at least one magnetoresistance element 540 in someembodiments. The other type of magnetic field sensing element, which maybe sensitive in a same direction or plane as magnetic field sensingelement(s) 540, may also be configured to generate a magnetic fieldsignal (e.g., magnetic field signal 540 a) in response to the appliedmagnetic field. The applied magnetic field, as may be sensed by magneticfield sensing element(s) 540, may be similar to the applied magneticfields discussed in the figures above and generated in various waysdepending on the type of sensor 530 and its application. As one example,the applied magnetic field may be generated in response to motion of theobject 120.

Signal path 150 is coupled to receive the magnetic field signal 540 a atan input and configured to generate a signal (e.g., digital signal 156a) representative of the magnetic field signal 540 a at an output. Inparticular, amplifier 152 of the signal path 150 is coupled to receivethe magnetic field signal 540 a and configured to generate an amplifiedsignal 152 a. Additionally, filter 154 of the signal path 150 is coupledto receive the amplified signal 152 a and configured to generate afiltered signal 154 a. Further, ADC 156 of the signal path 150 iscoupled to receive the filtered signal 154 a and configured to generatea corresponding digital signal 156 a. The digital signal 156 a isprovided to a corresponding input of controller 170.

Magnetic field sensing element(s) 1540, 2540 may be the same as orsimilar to magnetic field sensing element(s) 540 with each including atleast one magnetoresistance element. Each of magnetoresistance elements540, 1540, 2540 has at least one characteristic selected to provide arespective, different response to the applied magnetic field. The atleast one selected characteristic for each of elements 540, 1540, 2540may be the same or different. Additionally, signal paths 1150, 2150 maybe the same as or similar to signal path 150, as shown. Signal path 1150is coupled to receive a magnetic field signal 1540 a at an input andconfigured to generate a signal (e.g., digital signal 1156 a)representative of the magnetic field signal 1540 a at an output.Additionally, signal path 2150 is coupled to receive a magnetic fieldsignal 2540 a at an input and configured to generate a signal (e.g.,digital signal 2156 a) representative of the magnetic field signal 2540a at an output.

The controller 170 (i.e., processing circuitry) is coupled to receive atleast the digital signal 156 a, the digital signal 1156 a, and thedigital signal 2156 a at respective inputs and configured to generate acontroller output signal 570 a at an output of the sensor 530. Thecontroller output signal 570 a may be provided as a signal indicative ofat least one of the magnetic field signal 540 a, the magnetic fieldsignal 1540 a, and the magnetic field signal 2540 a (i.e., a signalindicative of the applied magnetic field). The controller output signal570 a may also be provided as a signal indicative of one or more of astrength of the applied magnetic field, a proximity of an object, anangle of the applied magnetic field, a current associated with theapplied magnetic field, and a movement (e.g., speed and/or direction) ofa ferromagnetic element (e.g., object 120) that affects the appliedmagnetic field. In some embodiments, the controller output signal 570 amay be received by circuitry (e.g., analog, digital or mixed-signalcircuitry) (not shown) for further processing (e.g., for generatingfiltered signals, amplified signals, and the like) and error reporting(e.g., to an engine control unit or ECU).

Additionally, in some embodiments, the controller 170 may be configuredto evaluate or poll (i.e., sample) each of magnetic field sensingelement(s) 540, 1540, 2540 (or outputs of each of magnetic field sensingelement(s) 540, 1540, 2540) at predetermined time periods through use ofone or more algorithms in the controller 170. As one example, thecontroller 170 may evaluate the outputs of the magnetic field sensingelement(s) 540, 1540, 2540 (i.e., may evaluate signals 156 a, 1156 a,2156 a) with one or more detectors (e.g., peak detectors). As long as atleast two of the outputs of the magnetic field sensing element(s) 540,1540, 2540 respond in a same or similar manner to the applied magneticfield (e.g., two detector outputs switch at substantially the sametime), as may be determined through one or more logic operations (e.g.,exclusive-or operation), for example, the controller 170 may provide anoutput signal (here, controller output signal 570 a) indicative of aspeed of motion of the object 120 or a direction of motion of the object120. In other words, as one result of each of the magnetic field sensingelement(s) 540, 1540, 2540 having at least one characteristic selectedto provide a respective, different response to the applied magneticfield, the output signal 570 a of the controller 170 is not affected (orat least is less affected) if one of the magnetic field sensingelement(s) 540, 1540, 2540 has an unexpected or undesirable response tothe applied magnetic field (e.g., due to a magnetic domain or theapplied magnetic field having a strength greater than a predeterminedlevel).

As described above and will be appreciated by those of ordinary skill inthe art, embodiments of the disclosure herein may be configured as asystem, method, or combination thereof. Accordingly, embodiments of thepresent disclosure may be comprised of various means including hardware,software, firmware or any combination thereof. Furthermore, embodimentsof the present disclosure may take the form of a computer programproduct on a computer-readable storage medium having computer readableprogram instructions (e.g., computer software) embodied in the storagemedium. Any suitable non-transitory computer-readable storage medium maybe utilized.

It is to be appreciated that the concepts, systems, circuits andtechniques sought to be protected herein are not limited to use in aparticular application but rather, may be useful in substantially anyapplication where it is desired to detect a magnetic field.

Having described preferred embodiments, which serve to illustratevarious concepts, structures and techniques, which are the subject ofthis patent, it will now become apparent to those of ordinary skill inthe art that other embodiments incorporating these concepts, structuresand techniques may be used. Additionally, elements of differentembodiments described herein may be combined to form other embodimentsnot specifically set forth above.

Accordingly, it is submitted that that scope of the patent should not belimited to the described embodiments but rather should be limited onlyby the spirit and scope of the following claims.

What is claimed is:
 1. A magnetic field sensor comprising a plurality of magnetoresistance elements, each having at least one characteristic selected to provide a respective, different response to an applied magnetic field, wherein each of the plurality of magnetoresistance elements is coupled in parallel.
 2. The magnetic field sensor of claim 1, wherein the respective, different responses of the plurality of magnetoresistance elements to the applied magnetic field differ in linearity.
 3. The magnetic field sensor of claim 1, wherein each of the plurality of magnetoresistance elements has a substantially similar resistance when the applied magnetic field has a magnetic field strength of about zero Gauss.
 4. The magnetic field sensor of claim 1, wherein at least one of the plurality of magnetoresistance elements experiences a non-linear response to the applied magnetic field.
 5. The magnetic field sensor of claim 4, wherein at least two of the plurality of magnetoresistance elements experience a non-linear response to the applied magnetic field.
 6. The magnetic field sensor of claim 4, wherein the non-linear response is a result of a magnetic domain.
 7. The magnetic field sensor of claim 4, wherein the non-linear response is a result of the applied magnetic field having a strength greater than a predetermined level.
 8. The magnetic field sensor of claim 1, wherein each of the plurality of magnetoresistance elements has a respective length and width and the length and width of the plurality of magnetoresistance elements comprises the at least one characteristic selected to provide the respective, different responses to the applied magnetic field, wherein the length and width of a first one of the plurality of magnetoresistance elements is a multiple of the length and width of a second one of the plurality of magnetoresistance elements.
 9. The magnetic field sensor of claim 8, wherein the length and width of the first one of the plurality of magnetoresistance elements is approximately one-half the length and width of a second one of the plurality of magnetoresistance elements.
 10. The magnetic field sensor of claim 1, wherein each of the plurality of magnetoresistance elements has a respective construction and wherein the respective construction comprises the at least one characteristic selected to provide the respective, different responses to the applied magnetic field.
 11. The magnetic field sensor of claim 10, wherein the respective construction comprises one or more of: a material of one or more layers of the magnetoresistance elements, a thickness of one or more layers of the magnetoresistance elements, an ordering of one or more layers of the magnetoresistance elements, and a spatial relationship of the magnetoresistance elements with respect to the applied magnetic field.
 12. The magnetic field sensor of claim 1, wherein the plurality of magnetoresistance elements are coupled in a bridge configuration.
 13. The magnetic field sensor of claim 1, further comprising processing circuitry responsive to a magnetic field signal generated by the plurality of magnetoresistance elements in response to the applied magnetic field and configured to provide an output signal of the magnetic field sensor indicative of the applied magnetic field.
 14. The magnetic field sensor of claim 13, wherein the output signal of the magnetic field sensor is indicative of one or more of a strength of the applied magnetic field, an angle of speed and/or direction of the applied magnetic field, a current associated with the applied magnetic field, and a movement of a ferromagnetic element that affects the applied magnetic field.
 15. The magnetic field sensor of claim 1, wherein the magnetic field sensor is a current sensor.
 16. The magnetic field sensor of claim 1, further comprising processing circuitry responsive to a plurality of magnetic field signals, each generated by a respective one or more of the plurality of magnetoresistance elements in response to the applied magnetic field and configured to provide an output signal of the magnetic field sensor indicative of the applied magnetic field.
 17. The magnetic field sensor of claim 16, wherein the output signal of the magnetic field sensor is indicative of one or more of a strength of the applied magnetic field, an angle of the applied magnetic field, a current associated with the applied magnetic field, and a speed and/or direction of movement of a ferromagnetic element that affects the applied magnetic field.
 18. The magnetic field sensor of claim 1, wherein the plurality of magnetoresistance elements comprise one or more of a giant magnetoresistance (GMR) element, a magnetic tunnel junction (MTJ) element and a tunneling magnetoresistance (TMR) element.
 19. The magnetic field sensor of claim 1, wherein the plurality of magnetoresistance elements comprise an anisotropic magnetoresistance (AMR) element.
 20. The magnetic field sensor of claim 1, further comprising a plurality of current sources, each coupled to one or more of the plurality of magnetoresistance elements.
 21. A method comprising providing each of a plurality of magnetoresistance elements with at least one characteristic selected to provide a respective, different response to an applied magnetic field, wherein each of the plurality of magnetoresistance elements is coupled in parallel.
 22. The method of claim 21, wherein providing each of a plurality of magnetoresistance elements comprises providing each of the plurality of magnetoresistance elements with a response to the applied magnetic field that differs in linearity.
 23. The method of claim 21, wherein providing each of a plurality of magnetoresistance elements comprises providing at least one magnetoresistance element that experiences a non-linear response to the applied magnetic field.
 24. The method of claim 23, wherein providing each of a plurality of magnetoresistance elements comprises providing at least two magnetoresistance elements that experience a non-linear response to the applied magnetic field.
 25. The method of claim 21, wherein providing each of a plurality of magnetoresistance elements comprises coupling the plurality of magnetoresistance elements in a bridge configuration.
 26. The method of claim 21, wherein providing each of a plurality of magnetoresistance elements comprises providing each of the plurality of magnetoresistance elements with a respective length and width and wherein the length and width of the plurality of magnetoresistance elements comprises the at least one characteristic selected to provide the respective, different responses to the applied magnetic field, and wherein the length and width of a first one of the plurality of magnetoresistance elements is a multiple of the length and width of a second one of the plurality of magnetoresistance elements.
 27. The method of claim 21, further comprising providing a plurality of current sources, each coupled to one or more of the plurality of magnetoresistance elements. 